1. Field of the Invention
The present invention relates to an electron emission device, and in particular, to an electron emission device which differentiates the distance of electron emission regions located at the central pixel region to the gate electrode from that of the electron emission regions located at the peripheral pixel region to the gate electrode.
2. Description of Related Art
Generally, electron emission devices are classified into a first type where a hot cathode is used as an electron emission source, and a second type where a cold cathode is used as the electron emission source.
Among the second type electron emission devices, known are the field emitter array (FEA) type, the metal-insulator-metal (MIM) type, the metal-insulator-semiconductor (MIS) type, the surface conduction emitter (SCE) type, and the ballistic electron surface emitter (BSE) type.
The electron emission devices are differentiated in their specific structure depending upon the types thereof, but basically have first and second substrates forming a vacuum vessel, an electron emission unit formed at the first substrate to emit electrons, and phosphor layers formed at the second substrate to emit light, to provide the desired display.
With the FEA type of electron emission device, electron emission regions are formed with a material capable of emitting electrons under the application of an electric field, and driving electrodes, such as cathode and gate electrodes, are placed around the electron emission regions. When an electric field is formed around the electron emission regions due to the voltage difference between the cathode and the gate electrodes, electrons are emitted from the electron emission regions.
With a typical structure of the FEA typed electron emission device, cathode electrodes, an insulating layer and gate electrodes are sequentially formed on the first substrate, and openings are formed at the insulating layer and the gate electrodes while partially exposing the cathode electrodes. Electron emission regions are formed on the cathode electrodes within the openings. With another typical structure of the FEA typed electron emission device, gate electrodes, an insulating layer and cathode electrodes are sequentially formed on the first substrate, and electron emission regions are formed at the lateral sides of the cathode electrodes.
With the above-structured FEA typed electron emission device, in order to increase the amount of emitted electrons under the application of a uniform electric field, as shown in FIG. 1, the distance of the respective electron emission regions 102 to the gate electrode 104 is kept the same, the reference numeral 106 of FIG. 1 indicating a gate hole. However, such a gate electrode structure involves leakage of light at the pixel neighbors due to beam spreading, and hence, deteriorated color representation occurs.
In order to solve such a problem, as shown in FIGS. 2A and 2B, it has been proposed that the distance of the electron emission regions 102 to the gate electrode 104′ in the left and right directions X-X′ should be differentiated from that of the electron emission regions 102 to the gate electrode 104′ in the upper and lower directions Y-Y′. Consequently, the electric field applied to the electron emission regions 102 becomes non-uniform, thereby preventing the electron beams from being spread. However, as compared to the structure shown in FIG. 1, such a structure involves a reduced amount of emitted electrons due to the application of a non-uniform electric field.